1. Field of the Invention
Embodiments of the present invention relate to devices and methods aiding in movement of people and objects in general including but not limited to a dolly, a cart, a fork lift, a hand truck, a roller skate and the like.
2. Related Art
Various devices for aiding in movement of people and objects along a surface have been proposed, in which rotatable wheels are attached to a structural body. When a force is applied in the desired direction of movement, the wheels rotate along the surface and decrease friction between the structural body and the surface.
Various different mechanisms and methods have been used for applying such a force, including a motor that connects, through a transmission or other linkage to one or more wheels, to impart a rotational force to the connected wheels. Other mechanisms have employed a rotary pedal configuration in which foot pedals are attached to a rotary sprocket and a chain or belt connects the sprocket to a wheel gear.
Wheel motion on such apparatuses is usually limited to rotational motion about an axis of rotation. However, wheels on a roller skate or in-line skate are moved up and down (relative to the riding surface), as the rider's legs are lifted and set down, to impart a motive force in a generally horizontal direction of travel. As a result of the up and down motion of the wheels during a skating motion, much force is exerted in a perpendicular direction to the movement of the apparatus, resulting in a considerable amount of wasted energy.
Previous inventions have attempted to remedy the problem, but either required complicated designs or required alteration of the conventional style of use of the device. Examples of previous designs are described in U.S. Pat. Nos. 1,208,173; 732,120; 1,924,948; 1,437,314; and, 1,784,761, each of which are incorporated herein by reference, in its entirety.